document.write( "Question 1007160: Let \"f%28x%29=+1%2F%282x%5E3-9%29\" and find \"f%5E-1%28x%29\" \n" ); document.write( "
Algebra.Com's Answer #623148 by Theo(13342)\"\" \"About 
You can put this solution on YOUR website!
f^-1(x) is the inverse function of f(x).\r
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\n" ); document.write( "\n" ); document.write( "let y = f(x).\r
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\n" ); document.write( "\n" ); document.write( "you get y = 1/(2x^3-9)\r
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\n" ); document.write( "\n" ); document.write( "replace y with x and x with y and you get:\r
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\n" ); document.write( "\n" ); document.write( "x = 1/(2y^3-9)\r
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\n" ); document.write( "\n" ); document.write( "that's your inverse equation.\r
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\n" ); document.write( "\n" ); document.write( "what's left is to solve for y if you can.\r
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\n" ); document.write( "\n" ); document.write( "if not, go with it the way it is.\r
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\n" ); document.write( "\n" ); document.write( "this one can be solved for y.\r
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\n" ); document.write( "\n" ); document.write( "start with x = 1/(2y^3-9)\r
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\n" ); document.write( "\n" ); document.write( "multiply both sides of the equation by (2y^3-9) and divide both sides of the equation by x.\r
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\n" ); document.write( "\n" ); document.write( "you will get:\r
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\n" ); document.write( "\n" ); document.write( "2y^3 - 9 = 1/x\r
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\n" ); document.write( "\n" ); document.write( "add 9 to both sides of the equation to get:\r
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\n" ); document.write( "\n" ); document.write( "2y^3 = 1/x + 9\r
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\n" ); document.write( "\n" ); document.write( "since 1/x + 9 is the same as (1+9x)/x, the equation becomes:\r
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\n" ); document.write( "\n" ); document.write( "2y^3 = (1+9x)/x\r
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\n" ); document.write( "\n" ); document.write( "divide both sides of the equation by 2 to get:\r
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\n" ); document.write( "\n" ); document.write( "y^3 = (1+9x)/(2x)\r
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\n" ); document.write( "\n" ); document.write( "take the third root of both sides of the equation to get:\r
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\n" ); document.write( "\n" ); document.write( "y = ((1+9x)/(2x))^(1/3)\r
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\n" ); document.write( "\n" ); document.write( "that's your inverse equation after you have solved for y.\r
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\n" ); document.write( "\n" ); document.write( "the grpah of the equation plus its inverse is shown below.\r
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\n" ); document.write( "\n" ); document.write( "the graphs also includes the line y = x which they need to be a reflection of in order to be inverse equations.\r
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\n" ); document.write( "\n" ); document.write( "the graph also includes lines y = -x + 5 and y = -x - 5 thst shows that the points are reflections about the line y = x.\r
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\n" ); document.write( "\n" ); document.write( "that's because (x,y) on the original equation equals (y,x) on the inverse equation.\r
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